A rapid and universal bacteria-counting approach using CdSe/ZnS/SiO2 composite nanoparticles as fluorescence probe

Xin Fu; Kelong Huang; Suqin Liu
February 2010
Analytical & Bioanalytical Chemistry;Feb2010, Vol. 396 Issue 4, p1397
Academic Journal
In this paper, a rapid, simple, and sensitive method was described for detection of the total bacterial count using SiO2-coated CdSe/ZnS quantum dots (QDs) as a fluorescence marker that covalently coupled with bacteria using glutaraldehyde as the crosslinker. Highly luminescent CdSe/ZnS were prepared by applying cadmium oxide and zinc stearate as precursors instead of pyrophoric organometallic precursors. A reverse-microemulsion technique was used to synthesize CdSe/ZnS/SiO2 composite nanoparticles with a SiO2 surface coating. Our results showed that CdSe/ZnS/SiO2 composite nanoparticles prepared with this method possessed highly luminescent, biologically functional, and monodispersive characteristics, and could successfully be covalently conjugated with the bacteria. As a demonstration, it was found that the method had higher sensitivity and could count bacteria in 3 × 102 CFU/mL, lower than the conventional plate counting and organic dye-based method. A linear relationship of the fluorescence peak intensity ( Y) and the total bacterial count ( X) was established in the range of 3 × 102–107 CFU/mL using the equation Y = 374.82 X − 938.27 ( R = 0.99574). The results of the determination for the total count of bacteria in seven real samples were identical with the conventional plate count method, and the standard deviation was satisfactory. [Figure not available: see fulltext.]


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